Integrated lance and strip for analyte measurement

ABSTRACT

The present invention relates, in general, to lancing elements for use in drawing bodily fluids out of a patient and, more particularly, to an improved lancing element including first and second elements positioned relative to each other such that an incision formed by the first element is held open by the second element and bodily fluids are pulled up the lancing element by surface tension on the first and second lancing elements.

CROSS-REFERENCE

[0001] This application claims priority to Provisional Application No.60/458,242 filed Mar. 28, 2003, which is incorporated herein byreference in its entirety.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] The present invention relates, in general, to lancing elementsfor use in drawing bodily fluids out of a patient and, moreparticularly, to an improved lancing element including first and secondelements positioned relative to each other such that an incision formedby the first element is held open by the second element and bodilyfluids are pulled up the lancing element by surface tension on the firstand second lancing elements.

[0004] 2. Description of the Related Art

[0005] Integrated skin lancing and body fluid analysis samplers areknown in the art. One such system is described and illustrated in WO02/49507. The integrated system described in WO 02/49507 includes alancing element or lance, which is attached to or integrated with a teststrip adapted to measure the quantity of an analyte in bodily fluid or,alternatively, some characteristic of the bodily fluid. Usable bodilyfluids may include, for example, blood or interstitial fluid (ISF). Thelancing element is used to make an incision in the skin and the bodilyfluid is drawn up the lancing element to the test strip by, for example,capillary action. Such integrated samplers may be combined with, forexample, an electrochemical meter and referred to as monolithic orin-situ sampling devices.

[0006] Many lancing devices have been devised to form incisions and toenable bodily fluids to be withdrawn from those incisions. Solid lancetsare used to open an incision in the skin to allow bodily fluids toescape to the surface of the skin where they can be sampled by thepatient or the doctor. In order to ensure that enough fluid is releasedfrom the incision, such solid lancing elements are generally larger indiameter to facilitate the flow of sufficient bodily fluids from theincision for sampling purposes. However, such solid needles generallyrely on the size of the incision to ensure that enough bodily fluids areexpressed and are not used to facilitate the flow of fluids to thetesting apparatus.

[0007] Hollow needles have also been described for use in drawing fluidsout of the body for testing purposes; such needles may have a pointed orbeveled end to facilitate opening the incision. In such needles, theincision is held open by the outer diameter of the needle to facilitatethe flow of bodily fluids out of the incision and the bodily fluids aredrawn up the needle either by a vacuum or by capillary action or by acombination of vacuum and capillary action.

[0008] Other lancing devices have been described wherein the lance is aflat or partially curved piece which includes an open channel forguiding fluid from the sharpened tip to the proximal end of the lance bymeans of, for example, surface tension and/or capillary action. Suchlacing elements are advantageous because of the ease of manufacture andthe ease of integrating them into, for example, a test strip, in orderto facilitate both lancing and measurement in a single element. Wherethe landing element is a flat or partially flat piece which includes anopen channel for guiding fluid, it is possible for the edges of theincision to close on the channel, fully or partially blocking thechannel and preventing bodily fluids from flowing to the proximal end ofthe channel or limiting the amount of fluid which can flow.

[0009] Problem to be Solved

[0010] It would, therefore, be advantageous to design a lancing devicewhere the lancing element is a flat or partially curved piece includingan open channel and the lancing element includes a separation elementfor holding the incision open when the lancing element is in the woundand preventing the edges of the incision from closing on the lancingelement and partially or fully blocking the open channel. It would beadvantageous to design a lancing device wherein the separation elementis positioned slightly proximal to the sharpened tip of the lancingelement to facilitate insertion of the lance into the skin. It wouldfurther be advantageous to design a lancing device wherein the lancingelement and the separation element are formed from a single metal sheet.It would further be advantageous to design a lancing device wherein thelancing element and the separation element are positioned opposite eachother such that fluid is pulled up the lancing element and into the openchannel by surface tension between the fluid and the lancing element andseparation element, thus facilitating the filling of the channel. Itwould further be advantageous to design a lancing device wherein thelancing element and the separation element are formed from a singlesheet of metal rolled to position the separation element opposite thelancing element such that the proximal end of the lancing element andthe separation element form an open channel. It would further beadvantageous to manufacture the lancing devices described herein using,for example, a metal forming or stamping process.

SUMMARY OF THE INVENTION

[0011] A lance according to the present invention includes a lancingelement having a first sharpened end point, a separation element havinga second sharpened end point wherein the second sharpened end point ispositioned proximal to the first sharpened end point, a connectorconnecting a proximal portion of the first lancing element to a proximalportion of the separation element, the connector forming a channel. In afurther embodiment of the present invention, the separation element ispositioned at an angle to the lancing element. In a further embodimentof the present invention the lancing element, the separation element andthe channel are formed from a single sheet of metal. In a furtherembodiment of the present invention, a space between the lancing elementand the separation element forms a gap, the gap increasing in sizeproximal to the second sharpened tip. In a further embodiment of thepresent invention, least a portion of the channel is treated with ahydrophilic surface coating. In a further embodiment of the presentinvention, at least a portion of the lancing element and at least aportion of the separation element are coated with a hydrophilic surfacecoating. In a further embodiment of the present invention, a proximalend of the channel is integrated into a sensor strip. In a furtherembodiment of the present invention, the sensor strip is connected at aproximal end thereof to a plurality of additional sensor strips

BRIEF DESCRIPTION OF THE DRAWINGS

[0012] While the novel features of the invention are set forth withparticularity in the appended claims, a better understanding of thefeatures and advantages of the present invention will be obtained byreference to the following detailed description that sets forthillustrative embodiments, in which the principles of the invention areutilized, and the accompanying drawings of which:

[0013]FIG. 1 is a perspective view of a lancing element and stripaccording to the present invention.

[0014]FIG. 2 is a perspective view of the top layer of a lancing elementand strip according to the present invention.

[0015]FIG. 3 is a perspective view of another embodiment of theinvention in which multiple strips form an array of sensors for use in acartridge format.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS OF THE INVENTION

[0016]FIG. 1 is a perspective view of lance 15 and sensor strip 100according to the present invention. In FIG. 1, lance 15 is connected tosensor strip 100. Sensor strip 100 may be, for example, a glucose sensorstrip which uses electrochemistry to measure the amount of glucose in abodily fluid, such as, for example, blood or interstitial fluid.Additionally, sensor strip 100 may be, for example, a coagulation sensorwhich measures a physical characteristic of a body fluid such asviscosity, capacitance, resistance, and the like. In FIG. 1, lance 15further includes lancing element 22 and separation element 24. Sensorstrip 100 further includes first electrode contact 10, adhesive layer11, conductive substrate 12, vent hole 13, second electrode contact 17,insulating substrate 18, insulating layer 20, registration hole 23 andworking electrode 36. In an embodiment of the invention, sensor strip100 may have an approximate width of 0.22 inches and an approximatelength of 0.55 inches.

[0017]FIG. 2 is a perspective view of lance 15 and the top layer ofsensor strip 100 for use in the present invention. In FIG. 2, the toplayer of sensor strip 100 and lance 15 is formed from conductivesubstrate 12. In the embodiment illustrated in FIG. 2, conductivesubstrate 12 includes vent hole 13 and registration hole 23. In FIG. 2,lance 15 includes lancing element 22, separation element 24 and fillchannel 21.

[0018] One embodiment of a lancing element and sensor strip suitable foruse in the present invention may be described with reference to FIGS. 1and 2. In the embodiment illustrated in FIGS. 1 and 2, sensor strip 100includes first electrode contact 10, wherein first electrode contact 10may be screen printed on an insulating substrate 18, and a secondelectrode contact 17, wherein second electrode contact 17 comprises aportion of conductive substrate 12 which is contiguous with referenceelectrode 37 and lance 15. In the embodiment of the lancing element andsensor strip illustrated in FIGS. 1 and 2, the orientation of firstelectrode contact 10 and second electrode contact 17 are arranged suchthat an analyte measurement meter, such as, for example, a glucose meter(not shown) can establish electrical contact with sensor strip 100. Inthe illustrated embodiment, first electrode contact 10 and secondelectrode contact 17 are arranged on the same side of insulatingsubstrate 18 to facilitate contact of both electrodes at the distal endof sensor strip 100.

[0019] Sensor strip 100 is manufactured using adhesive layer 11 toattach insulating substrate 18 to conductive substrate 12. Adhesivelayer 11 could be implemented in a number of ways, including usingpressure sensitive material, heat activated material, or UV cured doublesided adhesive material. Conductive substrate 12 may be, for example, asheet of electrically conductive material such as gold or platedstainless steel. The geometry of conductive substrate 12 may be formedby, for example, stamping process or photo etching. In the embodimentillustrated in FIGS. 1 and 2, lance 15 may be manufactured as anintegral part of conductive substrate 12. Vent hole 13, may be formedby, for example, punching through conductive substrate 12. Vent hole 13is used to facilitate the transport of bodily fluid up lance 15 andacross working electrode 36. Registration hole 23 may be formed duringthe stamping process of making conductive substrate 12.

[0020] In one embodiment of the invention, an analyte sensing layer maybe, for example, a glucose sensing layer, including an enzyme, a buffer,and a redox mediator. An analyte sensing layer (not shown) maypreferably be deposited on top of working electrode 36. Where an analytesensing layer is used to detect the presence and concentration ofglucose in a bodily fluid, at least a portion of glucose sensing layerdissolves in the bodily fluid and is used to convert the glucoseconcentration into an electrically measured parameter which isproportional to the glucose concentration in the sample.

[0021] In the embodiment illustrated in FIGS. 1 and 2, lance 15 has adistal and proximal end and the proximal end is integrated withreference electrode 37 and the distal end includes sharpened tip 38 atthe distal end of lacing element 22. Lance 15 may be formed by theprocess of stamping or photo-etching a conductive metal sheet.Photo-etching lance 15 is also beneficial in facilitating themanufacture of a lancing element which has a sharp lancing element 22and separation element 24. In a subsequent process step, lance 15,lancing element 22, and separation element 24 may be bent to form a “V”or “U” shaped channel geometry as shown in FIG. 2. Fill channel 21serves as a conduit from lancing element 22 and separation element 24 toworking electrode 36 and reference electrode 37. In one embodiment ofthe present invention, the distal end of lacing element 22 andseparation tip 40 of separation element 24 are offset by about 0.005inches to 0.020 inches.

[0022] The design of lance 15 is adapted to more effectively cut skindue to a sharper leading point of lancing element 22. As illustrated inFIG. 2, with separation tip 40 offset distally from sharpened tip 38 ofelement 22, the extreme distal end of lance 15 comprises only sharpenedtip 38 which may be a very sharp point or edge to facilitate the initialincision as lancing element 22 enters the skin. In contrast, if lancingelement 22 and separation element 24 were coincident, the leading pointof lance 15 would include both sharpened tip 38 and separation tip 40making the combination less sharp than the embodiment illustrated inFIG. 2 and requiring more force to create the initial incision. Theoffset of sharpened tip 38 and separation tip 40 make lance 15 moremanufacturable because it reduces the inherent alignment difficulties inbringing the sharp point of lancing element 22 and separation element 24into alignment or contact with each other. The embodiment of theinvention illustrated in FIGS. 1 and 2 is further beneficial because itenhances fluid egress by helping to spread and hold open the skin woundafter the initial incision is made. In the embodiment illustrated inFIGS. 1 and 2, the lance 15 further includes reference electrode 37 andsecond electrode contact 17. Alternative embodiments may include formingall of the electrodes and electrode contacts on insulating substrate 18.

[0023] In the embodiment of the invention illustrated in FIG. 2, lance15 includes fill channel 21, wherein the seamless transition between thelancing element 22 and separation element 24; and fill channel 21facilitates the flow of body fluid from the wound to working electrode36. Additionally, the seamless transition between the lancing element22, separation element 24 and fill channel 21 prevents the introductionof stop junctions which can impede the capillary flow rate of liquidsamples. The unique geometry increases the likelihood that a liquidsample will sufficiently cover working electrode 36 and referenceelectrode 37 regardless of the height of the lance 15 above or below theskin wound, or even if lance 15 lies horizontally offset from the wound.In certain embodiments of the invention, sample can be applied to theside of lance 15 rather than just the proximal end of lance 15 whichprovides a user the option of dosing sample onto sensor strip 100 aftera site has been lanced separately.

[0024] In the embodiment of the invention illustrated in FIG. 2, the gap42 between lancing element 22 and separation element 24 guides bodilyfluids into fill channel 21. The increasing separation between lancingelement 22 and separation element 24 as fluid moves distally towardsfill channel 21 facilitates the drawing of fluid into fill channel 21and from fill channel 21 to sensor strip 100. As gap 42 narrows towardsa distal end of separation tip 40 of separation element 24, the surfacetension between the bodily fluid in gap 42 and the walls of gap 42increases, thus bodily fluid is drawn more readily into gap 42, and upinto sensor strip 100. Gap 42 is also advantageous in that itfacilitates the introduction of bodily fluids into fill channel 21 byfacilitating the flow of bodily fluids positioned to the side of gap 42,thus enhancing the ways in which sensor strip 100 may be used to gatherbodily fluids.

[0025] Fill channel 21 may facilitate the flow of bodily fluids by, forexample, wicking or capillary action. In the embodiment illustrated inFIGS. 1 and 2, fill channel 21 has an open geometry which facilitatesthe wicking of viscous samples and provides for simpler manufacturingtechniques when compared with closed capillary channels. For certainembodiments of the invention, fill channel 21 may be coated with asurfactant coating or undergo a hydrophilic surface treatment toincrease the capillary force within fill channel 21. For certainembodiments of the invention separation element 24 and lancing element22 may be coated with a surfactant coating or undergo hydrophilicsurface treatment to increase the capillary flow force within gap 42.Additionally, the open geometry of fill channel 21 facilitates thewicking of sample because it prevents the formation of a vacuum block.In a closed channel geometry, a capillary inlet can become plugged if itis positioned too close to the wound or inside the wound preventing airfrom facilitating the flow of sample to the capillary. With the opengeometry of fill channel 21, the proximal end of lance 15 can bepositioned arbitrarily close to the source of the blood and allow forsufficient fill of sample. In this embodiment of the invention, the opengeometry of fill channel 21 has the capacity to hold a larger samplevolume than the minimum sample volume to cover reference electrode 37and working electrode 36. The open geometry of fill channel 21 thusallows excess sample to accumulate along fill channel 21 which helpsleave a cleaner wound site.

[0026] In the illustrated embodiment as shown in FIG. 2, the geometry ofreference electrode 37 may be formed during the stamping process whicheffectively embosses the surface of conductive substrate 12. Thestamping process may provide the pressure needed to create a recess inconductive substrate 12 which can help define the distance betweenreference electrode 37 and working electrode 36. For certainapplications of the described invention, it may be advantageous tocontrol the distance between reference electrode 37 and workingelectrode 36 by embossing conductive substrate 12 instead of controllingthe thickness of adhesive layer 11. For other applications of thedescribed invention, it may also be advantageous to not emboss theconductive substrate 12 and use adhesive layer 11 to help define thegeometry of reference electrode 37.

[0027] In the embodiment of sensor strip 100 illustrated in FIG. 1,insulating substrate 18 consists of material such as polyester orceramic on which a conductive material can be printed onto insulatingsubstrate 18 through silk-screening, sputtering, or electro-lessdeposition. Conductive material deposited on insulating substrate 18forms first electrode contact 10 and working electrode 36. Insulatinglayer 20 may be, for example, screen printed to form a boundary forfirst electrode contact 10 and working electrode 36.

[0028]FIG. 3 is a perspective view of another embodiment of theinvention in which multiple strips form an array of sensors for use in acartridge format. Such an array may be inserted into a meter (not shown)having strips dispensed in a serial manner, one by one. The format ofthis embodiment allows a row of strips to be folded in a manner similarto an accordion wherein several strips similar to sensor strip 100 inFIG. 1 are attached together on an arrangement which facilitates theiruse in a cartridge. In FIG. 3, conductive substrate 12 is stamped in aprogressive manner to form lance 15 such that several of them arechained together in series. The stamping process of conductive substrate12 forms index hole 31, neck 32, and contact hole 33.

[0029] In a further embodiment of the invention, a second electrodelayer (not shown) comprising an adhesive layer and glucose sensing layerwould be attached to conductive substrate 12 as illustrated in FIG. 3. Acontact area for a reference electrode for all of the strips within thearray may be formed using a single area within conductive substrate 12.However, individual contacts must be made for working electrode 36 forall of the strips within the array. In the embodiment of this invention,index hole 31 is used to index the strip cartridge so that it can move afresh strip to a test position. Neck 32 is punched in between 2 adjacentstrips. The purpose of neck 32 is to facilitate the strip bending at thelocation of neck 32. In order for the strip to be expressed such that auser can apply blood, the strip is bent downward and neck 32 facilitatesbending at a defined location. Contact hole 33 on conductive substrate12 allows electrical contact to be made with a working electrode on aninsulating substrate.

[0030] In a method of lancing in accordance with the present invention,a lance similar to the embodiments illustrated in FIGS. 1 through 3 isprovided having a lancing element 22 with a sharpened tip 38, aseparation element 24 having a separation tip 40 is positioned proximalto sharpened tip 38. In one embodiment of the invention the separationtip 40 may be positioned between approximately 0.005 inches and 0.020inches proximal to sharpened tip 38. A method according to the presentinvention further includes the step of providing a connector connectingthe proximal end of lancing element 22 to the proximal end of separationelement 24 wherein the connector forms a fill channel 21 extending fromthe proximal end of lancing element 22 and the proximal end ofseparation element 24 to a working electrode 36 of sensor strip 100. Themethod further including the steps of inserting the lancing element intoskin to form an incision, inserting the separation element 24 to furtheropen the incision and maintaining the position of the lancing element 22and the separation element 24 in the incision while blood or otherbodily fluids are drawn into a gap 42 between the lancing element 22and. separation element 24. The method further comprising the step ofdrawing the bodily fluids from gap 42 into fill channel 21.

[0031] A lance 15 constructed in accordance with the present inventionis beneficial due to the seamless transition between the tip section andthe capillary section, and because the tip itself is a type ofcapillary. The unique construction of this design better insures thatbodily fluids enter the fill channel 21 regardless of the height of thetip above or below the skin wound, or even if the tip lies horizontallyoffset from the wound, where the lance acts as a conduit for the bodilyfluids.

[0032] A sensor strip 100 constructed according to the present inventionis more easily by manufactured than a closed channel sensor strip. Sucha strip may be manufactured by, for example, injection molding,embossing, or chemical etching, or even simple machining. While thecapillary force of an open channel may be weaker than a comparableclosed channel, the weakness can be overcome with the use of, forexample, hydrophilic surface treatments or surfactant coatingsincluding: Tween-80, a product of Sigma Chemical Co., St. Louis, Mo.;Aerosol OT a product of Cytec Industries, West Paterson, N.J.; JBR-515,a product of Jeneil Biosurfactant Company of Saukville, Wis.; andNiaproof a product of Sigma Chemical Co., St. Louis, Mo.

[0033] A sensor strip 100 constructed according to the present inventionmay have improved transfer properties because the invention describedherein prevents the creation of a vacuum block in fill channel 21 thatwould prevent fluid from moving through the fill channel 21 and onto themeasurement pad. With a closed channel capillary, the inlet must bepositioned or designed to ensure that air is not prevented from freelyentering the capillary during transfer into the measurement area. Thus,in a closed channel system, if the inlet is positioned too close to thewound or even inside it, flow may be disrupted or stopped. With the openchannel of a sensor strip designed in accordance with the presentinvention, however, the inlet to the channel can be positionedarbitrarily close to the source of the blood.

[0034] Another advantage of a strip in accordance with the presentinvention including an open channel is that such a strip has thecapacity to hold a larger volume of fluid than the minimum required tofill and initiate transfer into the measurement pad. One embodiment ofthe present invention the minimum volume required to fill the lance suchthat the column of fluid reaches the measurement pad is approximately230 nL. However, lancing may produce quantities which are greater than230 nL. Because of the open channel form in the present invention, theexcess blood that is presented to the lance will continue to accumulatealong the lance channel, forming a bulging drop of blood. This propertyis useful in that it clears away excess blood from the skin, leaving acleaner lance wound.

[0035] Another advantage of the open channel design in accordance withthe present invention is that a drop of fluid can be applied to the sideof the lance rather than just at the tip of the lance (i.e. in a closedchannel there is a distinct area where fluid must be presented to bedrawn into the capillary. Manual application of blood might be requiredif the blood comes from a site that has been lanced separately. Thus,using a sensor strip designed in accordance with the present invention,provides the option of ‘side’ filling increases the user's options.

[0036] In one embodiment of the present invention, the stamped metal ofconductive substrate 12 could also serve as a working or counterelectrode. A unique aspect of the sheet metal design used in the presentinvention is the fact that it also allows the assembly to be constructedwith first electrical contact 10 and second electrode contact 17 on thesame side of the strip. This greatly simplifies the requirements formating contacts on a meter because conductive substrate 12 comprises asolid conductor allowing electrical contact to be established from boththe top and bottom side of conductive substrate 12, wherein the top sideof conductive substrate 12 is on the same side as second electricalcontact 17 and the bottom side of conductive substrate is on the sameside as reference electrode 37.

[0037] On a conventionally constructed electrochemical strips using afacing electrode arrangement where both working and reference electrodesare printed or applied onto an insulating substrate, the electricalcontacts must be positioned on opposites sides of the strip making themeter contacts more complex. If reference electrode 37 was printed orapplied onto an insulating substrate, conductive substrate 12 would beinsulated on the top side preventing electrical connection to beestablished from the top side. It could be possible to establishelectrical connection from the top side if there was a partial removalof insulation from conductive substrate 12, however, this would addadditional complexity to the manufacturing of the strip.

[0038] Finally, because sheet metal forming can be done as a progressivedie stamping, in a strip designed in accordance with the presentinvention with individual lances chained together in series, it could bepossible to construct an array of test sensors with a single, commonreference thus requiring just one contact.

[0039] It will be recognized that equivalent structures may besubstituted for the structured illustrated and described herein and thatthe described embodiment of the invention is not the only structurewhich may be employed to implement the claimed invention. In addition,it should be understood that every structure described above has afunction and such structure can be referred to as a means for performingthat function.

[0040] While preferred embodiments of the present invention have beenshown and described herein, it will be obvious to those skilled in theart that such embodiments are provided by way of example only. Numerousvariations, changes, and substitutions will now occur to those skilledin the art without departing from the invention.

[0041] It should be understood that various alternatives to theembodiments of the invention described herein may be employed inpracticing the invention. It is intended that the following claimsdefine the scope of the invention and that methods and structures withinthe scope of these claims and their equivalents be covered thereby.

What is claimed is:
 1. A lance comprising: a lancing element having afirst sharpened end point; a separation element having a second endpoint wherein said second end point is positioned proximal to said firstsharpened end point; a connector connecting a proximal portion of saidlancing element to a proximal portion of said separation element, saidconnector forming a channel.
 2. A lance according to claim 1, whereinsaid separation element is positioned at an angle to said lancingelement.
 3. A lance according to claim 1, wherein said lancing element,said separation element and said channel are formed from a single sheetof metal.
 4. A lance according to claim 1, wherein a space between saidlancing element and said separation element forms a gap, said gapincreasing in size proximal to said second end point.
 5. A lanceaccording to claim 1, wherein at least a portion of said channel istreated with a hydrophilic surface coating.
 6. A lance according toclaim 5, wherein at least a portion of said lancing element and at leasta portion of said separation element are coated with a hydrophilicsurface coating.
 7. A lance in accordance with claim 1, wherein aproximal end of said channel is integrated into a sensor strip.
 8. Alance in accordance with claim 7, wherein said sensor strip is connectedat a proximal end thereof to a plurality of additional sensor strips.ELEMENTS 10 1st electrode contact 11 adhesive layer 12 Conductivesubstrate 13 vent hole 15 Lance 17 2^(nd) electrode contact 18insulating substrate 37 reference electrode 20 insulating layer 21 fillchannel 22 lancing element 23 Registration hole 24 Separation element 31Index hole 32 Neck 33 Contact hole 36 Working electrode 38 Sharpened tip40 Separation tip 42 Gap 100 sensor strip